On Saturday Kaufman Country district attorney Mike McLelland and his wife Cynthia were found shot dead in their house.

Mr McLelland in interview shortly after the murder of Colorado's prison chief Tom Clemments last month, said it was possible he had been gunned down by a white supremacist gang.

Mr McLelland said his office had prosecuted several cases against racist gangs, who have a strong presence around Kaufman County, a mostly rural area with a population of about 104,000.

"We put some real dents in the Aryan Brotherhood around here in the past year," he said.

Mr McLelland said he carried a gun everywhere around town, a commuter community for the Dallas area. He thought assassins were more likely to try to attack him outside. He said he had warned all his employees to be constantly on the alert. "The people in my line of work are going to have to get better at it," he said of dealing with the danger, "because they're going to need it more in the future."

The number of attacks on prosecutors, judges and senior law enforcement officers in the US has risen in the past three years.

Tarrant County district attorney Joe Shannon said his staff has been cautioned, but he declined to discuss the specific security measures that have been taken. Harris County district attorney Mike Anderson said he accepted the Houston sheriff's offer of 24-hour security for him and his family after learning about the killings. He said he also would take precautions at his office, the largest one in Texas, which has more than 270 prosecutors. "I think district attorneys across Texas are still in a state of shock," he said.

Kaufman County sheriff David Byrnes said said security would be stepped up at the local court, but he refused to say what other steps might be taken.

Mr McLelland, 63, is the 13th prosecutor killed in the US since the National Association of District Attorneys began keeping count in the 1960s.